1. Field of the Invention
This invention relates to a fast hardening aqueous coating composition which can be utilized in applications where it is desirable to form a hard, smear-resistant, non-tracking surface very quickly after deposit of the coating under ambient conditions. In particular, the invention relates to fast hardening aqueous traffic marking paint, which forms a hard, smear-resistant surface very soon after application under ambient conditions to a surface, such as a roadway, and which allows the resumption of normal traffic with minimal interruption.
2. Description of the Related Art
Conventional traffic marking paints have been required to provide hard, durable surfaces that will stand up to rough treatment from road traffic, and also to dry as fast as possible under ambient conditions, so that any diversion of traffic from the roadway is, minimized. These and other conventional fast dry systems have used volatile organic solvent (VOC) based compositions which are easy to apply and which evaporate quickly to leave the desired hard, smear-resistant coating. However, unless contained, the organic solvent used in these coatings evaporates into the environment, and, in the case of traffic paint, containment is not feasible. As the volume of fast drying compositions used increases, the release of VOC""s into the environment becomes increasing costly and ever less desirable. Suitable water based fast drying compositions would be very desirable.
The drying of conventional water based compositions depends upon the evaporation of water from the composition. This is generally quite slow in comparison to the drying of an organic solvent based system due to the much higher heat of vaporization of water in comparison to typical organic solvents.
Generally, three techniques have been used to accelerate the drying of traffic paint. The paint may be heated as it is applied. Alternatively, the paint may be formulated at very high solids, thereby decreasing the amount of water in the paint which must evaporate.
A third, less common approach is to cause the paint to harden before all of the water is gone. In this case, the paint may have the appearance, feel, and non-tracking characteristics of dry paint, even though significant water remains in the composition. This approach uses what, in reality, is a fast hardening paint composition.
U.S. Pat. Nos. 4,119,600 and 4,199,400 disclose migration resistant binders useful in bonding non-woven fibers to form composites, which binders can be prepared from (a) an anionically stabilized latex, (b) a water soluble polymer containing a plurality of amine groups formed from at least one ethylenically unsaturated monomer, and (c) a volatile base.
EP Patent Application 409,459 discloses and claims an aqueous coating composition comprising an anionically stabilized polymer latex, a polyfunctional amine polymer and a volatile base. This composition is described as quick drying.
EP Patent 066,108 discloses a road marking material based on an aqueous plastic dispersion which is free of organic solvents.
EP Patent Application 525,977 discloses and claims a waterborne paint for traffic marking comprising a multipolymer micellar system.
PCT Application WO 92/17543 discloses post-extended anionic acrylic dispersions intended for use as a base coat of a multi-layer automotive coating, which are formed by the reaction of carboxylic acid groups of an acrylic resin with an organic compound having at least two oxirane groups.
U.S. Pat. No. 3,639,327 discloses an improved adhesive system which employs a small amount of polyethylenimine as a cationic zeta potential agent in a latex composition.
U.S. Pat. Nos. 4,049,869 and 4,082,884 disclose a composition consisting of an aqueous solution or dispersion of a carboxylated hydrophilic acrylic polymer, a crosslinking agent for the polymer, and an ultraviolet absorbing agent.
U.S. Pat. No. 3,806,485 discloses a stable liquid dispersion of a water soluble anionic vinyl addition polymer and a water soluble cationic polymer such as an alkylene polyamine.
U.S. Pat. No. 4,980,404 discloses one-component adhesives for adhesive bonds having increased high-temperature strengths containing aqueous dispersions of carboxyl-containing polyacrylates and organic polyamino compounds having a molecular weight of from 250 to 15,000 and an amino functionality greater than 5.
Japanese Patent disclosure J51059928 discloses a coating composition comprising a cationic polymer electrolyte such as polyethylene imine and an ammonium or organic amine salt of a copolymer dispersion.
The prior art provides only partial solutions to the problems in this area, especially, in the area of fast drying compositions. It is desirable in a composition for many uses that it be fast drying and water based, so that it may replace alkyl based systems with their unacceptably high release of VOC""s. Low viscosity of the composition and high water resistance of the coating produced from the composition are also desirable, as is commercial availability of all of the ingredients necessary for production of the composition.
In the area of traffic marking paint, it would be desirable to have economical water based compositions that harden quickly enough for traffic to be routed over them soon after application, and which provide superior characteristics, such as increased water resistance, in the finished coatings produced therefrom.
The objects of the present invention are to provide a coating and binder system that is water based and low in VOC""s, one that hardens very quickly and that provides the resilience and smear-resistance of a dry coating while in the hard state before it has become significantly dehydrated. Hardening of the coating system is achievable under ambient conditions without elevated temperatures or other extraordinary means.
The present invention is related to a fast hardening aqueous coating composition comprising:
(a) from about 95 to about 99 weight percent, based on the weight of dry materials in the composition, of an anionically stabilized aqueous emulsion of a copolymer having a Tg of from about 0xc2x0 C. to about 40xc2x0 C., the copolymer comprising in polymerized form a polymerization mixture containing two or more ethylenically unsaturated monomers, wherein, based on the total weight of all ethylenically unsaturated monomers in the polymerization mixture, from 0 to about 4 weight percent of the monomers are xcex1,xcex2-ethylenically unsaturated aliphatic carboxylic acid monomers;
(b) from about 0.2 to about 5 weight percent of a polyimine having a molecular weight of from about 250 to about 20,000; and
(c) from about 0.2 to about 5 weight percent of a volatile base;
wherein the composition has a pH from about 8 to about 11, and wherein a cast film of the composition has a hardening rate measurement rating of at least 5 within 20 minutes after casting under ambient conditions of temperature up to 30xc2x0 C. and relative humidity no less than 50 percent.
This invention further relates to an aqueous coating composition comprising:
(a) from about 95 to about 99 weight percent, based on the weight of dry materials in the composition, of an anionically stabilized aqueous emulsion of a copolymer having a Tg of from about 0xc2x0 C. to about 40xc2x0 C., the copolymer comprising in polymerized form a polymerization mixture containing two or more ethylenically unsaturated monomers, wherein, based on the total weight of all ethylenically unsaturated monomers in the polymerization mixture, from 0 to about 4 weight percent of the monomers are xcex1,xcex2-ethylenically unsaturated aliphatic carboxylic acid monomers;
(b) from about 0.2 to about 5 weight percent of a polyimine having a molecular weight of from about 250 to about 20,000; and
(c) from about 0.2 to about 5 weight percent of a volatile base;
wherein the composition has a pH from about 8 to about 11, and wherein a pigment-containing formulation prepared from the composition has a no track time according to ASTM D711-84 of 20 minutes or less.
In another embodiment, the invention relates to a process for the preparation of a fast hardening aqueous coating composition comprising:
(1) preparing from about 95 to about 99 weight percent, based on the weight of dry materials in the composition, of an anionically stabilized aqueous emulsion of a copolymer having a Tg of from about 0xc2x0 C. to about 40xc2x0 C., the copolymer comprising in polymerized form a polymerization mixture containing two or more ethylenically unsaturated monomers, wherein, based on the total weight of all ethylenically unsaturated monomers in the polymerization mixture, from 0 to about 4 weight percent of the monomers are xcex1,xcex2-ethylenically unsaturated aliphatic carboxylic acid monomers;
(2) adding from about 0.2 to about 5 weight percent of a volatile base to the emulsion from (1) so that the pH of emulsion is in the range from about 8 to about 11;
(3) mixing with the product from (2) from about 0.2 to about 5 weight percent of a polyimine having a molecular weight of from about 250 to about 20,000;
wherein the composition has a pH from about 8 to about 11, and wherein a cast film of the composition has a hardening rate measurement rating of at least 5 within 20 minutes after casting under ambient conditions of temperature up to 30xc2x0 C. and relative humidity no less than 50 percent.
Within the scope of this invention is an embodiment relating to a fast hardening aqueous traffic paint comprising:
(1) a fast hardening aqueous coating composition comprising:
(a) from about 95 to about 99 weight percent, based on the weight of dry materials in the composition, of an anionically stabilized aqueous emulsion of a copolymer having a Tg of from about 0xc2x0 C. to about 40xc2x0 C., the copolymer comprising in polymerized form a polymerization mixture containing two or more ethylenically unsaturated monomers, wherein, based on the total weight of all ethylenically unsaturated monomers in the polymerization mixture, from 0 to about 4 weight percent of the monomers are xcex1,xcex2-ethylenically unsaturated aliphatic carboxylic acid monomers;
(b) from about 0.2 to about 5 weight percent of a polyimine having a molecular weight of from about 250 to about 20,000; and
(c) from about 0.2 to about 5 weight percent of a volatile base;
(2) an organic or inorganic pigment;
wherein the paint has a no track time according to ASTM D711-84 of 20 minutes or less.
In another embodiment, this invention relates to a fast hardening aqueous migration-resistant binder composition comprising:
(1) a fast hardening aqueous coating composition comprising:
(a) from about 95 to about 99 weight percent, based on the weight of dry materials in the composition, of an anionically stabilized aqueous emulsion of a copolymer having a Tg of from about 0xc2x0 C. to about 40xc2x0 C., the copolymer comprising in polymerized form a polymerization mixture containing two or more ethylenically unsaturated monomers, wherein, based on he total weight of all ethylenically unsaturated monomers in the polymerization mixture, from 0 to about 4 weight percent of the monomers are xcex1,xcex2-ethylenically unsaturated aliphatic carboxylic acid monomers;
(b) from about 0.2 to about 5 weight percent of a polyimine having a molecular weight of from about 250 to about 20,000; and
(c) from about 0.2 to about 5 weight percent of a volatile base; and
(2) an organic filler, an inorganic filler, an organic fiber, an inorganic fiber, or a mixture thereof.